During controlling a permanent magnet synchronous motor, it needs to suppress a speed fluctuation occurring during operation of the permanent magnet synchronous motor. The suppression of the speed fluctuation may relatively suppress a noise and a vibration, improve a comfort of a user, and prevent an occurrence of an out-of-step of the motor under abrupt change of load.
In the related art, there are at least following problems in the control of the permanent magnet synchronous motor:
1. Since a bandwidth of a speed loop is lower, the out-of-step may occur easily under abrupt change of load, and the speed fluctuation is big, which takes a long time to stabilize the speed. Thus, the existing control method is not applicable in some special occasions such as a servo motor control. At present, a conventional practice is to increase the bandwidth of the speed loop. However, it may cause problems that a speed ripple is big, a speed overshoot is easy to occur, and there is no bandwidth which is suitable for whole frequency bands and various load conditions.
2. A periodic load may lead to the speed fluctuation of the motor, such as a speed fluctuation caused by a compressor, and if this speed fluctuation is not suppressed, a vibration may be generated, and if an air conditioner is running for a long time in a case of large vibration, a pipe crack may be easy to occur and a quality of the air conditioner may be affected seriously.
Therefore, there is a need to improve the control technology of the permanent magnet synchronous motor.